Figure 2

Specificity of individual restriction fragments and patterns based on exact and experimental sizing tolerance. (a) HindIII restriction fragment specificity for the human genome for fragments within the experimental size range of 500 bp to 30 kb. For a given fragment size, the vertical scale represents the fraction of fragments in the genome that are indistinguishable by size in the case of either exact sizing (fragments in common between two fingerprints must be of identical size) or within experimental tolerance (fragments in common between two fingerprints must be within experimental sizing error; Figure 3) on a fingerprinting gel. When sizing is exact, fragment specificity follows approximately the exponential distribution of fragment sizes and spans a range of 3.5 orders of magnitude. When experimental tolerance is included, the number of distinguishable fragment size bins is reduced and the range of fragment specificity drops to two orders of magnitude. (b) The specificity of a fingerprint pattern of a given size in the human genome. Fingerprint pattern size is measured in terms of number of fragments. Regions with identical patterns are those in which there is a 1:1 mapping within tolerance between all sizeable fragments. The specificity of experimental fingerprint patterns is cumulatively affected by specificity of individual fragments. The specificity of fragments is sufficiently low (that is, due to high experimental precision) so that 96.5% of the genome is uniquely represented by fragment patterns of 8 fragments or more.